The error most commonly taught and/or practised relates to the down swing from the 'throw'. (Just to clarify also, an aerial is a position, not an action. You 'throw' to aerial position. Or is you read the Boyd technique, you "Zephyr" to one of three aerial positions).

The down swing of the leg should be used to create the swivel on the ball of foot, not to progress. The progression forward is created after the swivel via a further lowering into the hips, knees and ankles.